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  <title>Document</title>
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    /* text-decoratio 可以设置文本的装饰线 */
    .a1 {
      text-decoration: none;
    }
    .div1{
      text-decoration: underline;
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    .div2{
      text-decoration: line-through;
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    .div3{
      text-decoration: overline;
    }
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<body>
  <a href="">a元素自带下划线</a>
  <a class="a1" href="">去掉默认下划线</a>
  <div class="div1">添加下划线</div>
  <div class="div2">添加中划线</div>
  <div class="div3">添加上划线</div>
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